1. Field of the Invention
The present invention relates generally to an outboard drive for propelling a boat and more particularly, to an electric outboard drive that is lightweight and low-pollution.
2. Description of the Related Art
An outboard drive for attaching to the transom of a boat is a propulsion system adapted to be especially used for small watercrafts, such as pneumatic boats and speedboats. To date, most of the outboard drives utilize gasoline engines as their power source. However, the gasoline engine will produce loud noise when it is running and the exhausted waste gas after combustion of gasoline will adversely affect the health of passages and the environment. In addition, the gasoline engine may discharge oil soil, which will contaminate water. Therefore, the outboard drives adopting gasoline engine as power source may be an unpopular option because they can hardly meet the environment protection requirements nowadays. Further, in order to effect the steering control of the boat, the outboard drive needs to be equipped with a steering mechanism, which is usually complicated in its structure, thereby raising the manufacturing coats. Furthermore, conventional gasoline engines are heavy in weight; therefore, they can not be conveniently detached from the boat for transportation and storage, thereby increasing the risk of being stolen.
U.S. Pat. No. 7,614,925 disclosed a transportable outboard motor which utilizes an electric motor as its power source. Using an electric motor substituting for the gasoline engine is an environmentally friendly option that can improve the above-mentioned disadvantages of the gasoline-powered outboard drive. However, in the aforesaid US patent, the electric motor is configured to be installed inside the pylon that has a limit space, which in turn limits the specifications of the electric motors that can be used in this design, i.e. a big electric motor having a relatively big power output may not be used in the aforesaid design. This setup limits the power output of the outboard drive, resulting in that the power output provided by this kind of electric outboard motor may be insufficient for a lager boat.